Composition comprising polypropylene and an organosilicon compound

ABSTRACT

WHEREIN R&#39;&#39;, R&#39;&#39;&#39;&#39; and R&#39;&#39;&#39;&#39;&#39;&#39; are each a hydrogen atom, an alkyl radical of 1-18 carbon atoms, an aralkyl radical of less than 19 carbon atoms or O3SiCH2 - where Q is alkyl, alkenyl or aryl of less than 19 carbon atoms, at least one R&#39;&#39;, R&#39;&#39;&#39;&#39; or R&#39;&#39;&#39;&#39;&#39;&#39; being Q3SiCH2-, or (c) mixture of (a) and (b). The production of shaped polypropylene articles by melt extrusion of thermally degraded isotactic polypropylene can be carried forward at lower temperatures than were heretofore required by incorporating in the polypropylene prior to thermal degradation thereof, from 0.01 to 5 percent by weight, based on the weight of the polypropylene, or (a) a silane or siloxane having at least one *SiCH2NR2 group where R is hydrogen or a hydrocarbon radical, (b) an organosilicon compound of the general formula

" [58]" Field nrs'earen nited States Patent [191 Owen et al.

154] COMPOSITION COMPRISING POLYPROPYLENE AND AN ORGANOSILICON COMPOUND [75] Inventors: William J. Owen, Penarth; Bryan E.

Cooper, Bridgend, both of Wales [7 3] Assignee: Midland Silicones Limited, Reading,

Berkshire, England [22] Filed: July 20, 1970 [21] Appl. No.: 56,659

[30] Foreign Application Priority Data 52 user ..260/93.7, 260/45.7 R, zoo 94.9 013, 260/949 on 51 Int. Cl ..c0sr 29 9 2, 00 45/58, cosr 45/60 260/949 GD, 93.7, 45.7 R, 94.7 N

I 1- ar. 27,1973

FOREIGN PATENTS OR APPLICATIONS 246,827 11/1969 U.S.S.R ..260/94.9 (i D Primary Examiner-James A. Seidleck Assistant Examiner-William F. Hamro'ck Attorney-Robert F. Fleming, Jr., Laurence R. l-lobey and Howard W. Hermann [57] ABSTRACT The production oi shaped polypropylene articles by melt extrusion of thermally degraded isotactic polypropylene can be carried forward at lower temperatures than were heretofore required by incorporating in the polypropylene prior to thermal degradation thereof, from 0.01 to 5 percent by weight, based on the weight of the polypropylene, or (a) a silane or siloxane having at least one SiCI-I NR group where R is hydrogen or a hydrocarbon radical, (b) an organosilicon compound of the general formula wherein R, R and R' are each a hydrogen atom, an alkyl radical of 1-18 carbon atoms, an aralkyl radical of less than 19 carbon atoms or O SiCl-l where Q is alkyl, alkenyl or aryl of less than 19 carbon atoms, at leastone R', R" or R being Q SiCl'l or (c) mixture of (a) and (b). i

3 Claims, No Drawings COMPOSITION COMPRISING POLYPROPYLENE AND AN ORGANOSILICON COMPOUND This invention relates to improvements in or relating to the melt extrusion of polypropylene and relates in particular to the melt spinning of polypropylene having a stereoregular structure.

It is well-known to prepare shaped articles by the melt extrusion of polypropylene. In particular it is known to prepare filaments of polypropylene by the melt spinning of crystalline, that is isotactic, polypropylene. In order to improve the tensile characteristics of the filament it is usual to subject the filament after melt spinning and quenching to drawing at elevated temperatures to orient the filament. It is also known that filaments of polypropylene having high tenacities may be produced by degrading the polypropylene by drastic thermal treatment, that is by exposure to temperatures of about 260C or above, prior to extrusion through the filament-forming orifice. The use of such high temperatures however introduces considerable processing difficulties since they approximate closely to the temperature at which the polypropylene chars and is rendered unsuitable for use. We have now discovered that certain organosilicon compounds have the effect of lowering the temperature at which a given degree of degradation occurs in polypropylene, thereby permitting the melt spinning of polypropylene into high tenacity fibers and filaments under less severe thermal conditions.

It is an object of this invention to introduce an improved method for melt extruding polypropylene. Another object is a method for melt extrusion of polypropylene wherein the required polypropylene degradations can be carried forward at a lower temperature than heretofore required. Other objects and advantages of the invention are detailed in, or will be apparent from the disclosure and claims following.

This invention provides a process for the production of a shaped article by the melt extrusion of thermallydegraded isotactic polypropylene wherein the thermal degradation of the polypropylene is carried out in the presence of from 0.01 to 5 percent by weight based on the weight of polypropylene, of (a)'an organosilicon compound which is an organosilane or organosiloxane having at least one silicon-bonded group of the general formula --Ci-l NR wherein each R represents a hydrogen atom or a monovalent-hydrocarbon radical, (b) an organosilicon compound of the general formula wherein R, R" and R each represent a hydrogen atom, an alkyl radical having up to 18 carbon atoms, an aralkyl radical having up to 18 carbon atoms or a Q, SiCl-I, group, wherein 0 represents an alkyl, alkenyl or aryl radical having up to 18 carbon atoms, at least one of R, R" andR being the Q, SiCH, group, or (c) mixtures of(a) and (b).

In a further aspect the invention also includes a thermally-degradable composition comprising isotactic polypropylene and from 0.01 to 5 percent by weight of one or more of the specified organosilicon compounds (a) and (b).

As the organosilicon compound there can be employed any organosilane or organosiloxane containing the grouping Cl-l NR bonded to at least one silicon atom. In said group, each R represents a hydrogen atom or monovalent hydrocarbon radical, for example the methyl, ethyl, t-butyl, hexyl, octadecyl, vinyl, phenyl, tolyl or benzyl radical. Preferred as the organosilicon compounds (a) are the organosilanes and the sub stantially linear polydiorganosiloxanes of low molecular weight, for example the di triand tetrasiloxanes having therein the specified -CH, NR groups, any other substituents on the silicon atoms being monovalent hydrocarbon or halohydrocarbon radicals and oxygen atoms present as siloxane (Si O Si) linkages.

Most preferably the organosilicon compounds (a) have the general formula wherein each A represents a radical having from 1 to 18 carbon atoms and is a monovalent hydrocarbon radical, an alkoxy radical, an alkoxyalkyl radical, an alkoxyaryl radical or an alkoxyalkoxy radical, n is 0, l, 2 or 3 but is preferably 3 and R is as hereinabove defined. As the A radicals in the general formula there may be present one or more of alkyl radicals, for example methyl, ethyl, propyl, butyl, decyl and octadecyl, alltenyl radicals such as vinyl and allyl and aryl radicals such as phenyl, naphthy], tolyl and benzyl. The A radicals can also comprise alkoxy radicals, for example methoxy, ethoxy and propoxy radicals and alkoxy alkyl, alkoxyaryl and alkoxyalkoxy radicals for example methoxyethyl, ethoxypropyl, methoxyphenyl and methoxyethoxy radicals. Preferably however A is an alkyl radical having less than 9 carbon atoms or a phenyl radical.

For optimum results it is believed that the organosilicon compounds should be compatible, at least to some extent, with the isotactic polypropylene and some adjustment of the compatibility of the particular type of compound chosen can be achieved by variation of the A radicals.

Some of the organosilicon compounds (a) employed in the process of this invention are well-known materials and others can be prepared according to the method described in U.S. Pat. No.3,504,007.

The organosilicon compounds (b) which can be employed to assist in the degradation of polypropylene according to this invention may be broadly termed as silyl-substituted phenols. They are more particularly described by the general formula wherein R, R" and R' each represent a hydrogen atom or an alkyl or aralkyl radical having up to 18 carbon atoms, for example the methyl, ethyl, propyl, t-butyl, hexyl, dodecyl, benzyl or 2-phenyl ethyl radical, or a Q SiCl-i group wherein each Q represents an alkyl, alkenyl or aryl radical having up to 18 carbon atoms. At least one of R, R" and R' should be the Q SiCH radical, examples of which are the trimethylsilylmethyl, diphenylmethylsilylmethyl, vinyldimethyl silylmethyl and dimethylbenzylsilylmethyl radicals. The preferred compounds (b) are those wherein the radicals represented by R, R" R' and Q are selected from alltyl radicals having less than 9 carbon atoms and phenyl radicals.

organosilicon compounds (b) can be prepared, for example, by the reaction in the presence of magnesium of a phenolic compound having substituted therein a halomethyl group with an organosilicon compound Q Sil-lal wherein Q is as hereinabove defined and Hal represents a halogen atom, preferably the chlorine or bromine atom. Such a method is more completely described in our co-pending U.S. application Ser. No. 752,790, filed Aug. 15,1968.

Although applicable in the production of any shaped article such as sheets, by melt extrusion, the process of this invention finds particular application in the formation of fibers and filaments of polypropylene by melt spinning. In common with known techniques the fibers or filaments can be quenched following spinning and are then subjected to drawing at elevated temperatures to being about orientation of the fiber or filament to provide the desired high tensile properties.

In addition to assisting the thermal degradation of polypropylene at temperatures above about 180C the organosilicon compounds (a) and (b) employed herein also function to stabilize the polypropylene against oxidation at temperatures up to about 120 150 C. The use of the organosilicon compounds according to this invention therefore performs the dual function of assisting in the formation of high tenacity fibers and films during the melt spinning operation and subsequently serves to protect the spun fiber against oxidation at lower temperatures.

The following examples illustrate the invention.

Example 1 To a series of 2 kg. samples of isotactic polypropylene granules were added 25 ml. solutions in pentane of the following compounds, the concentration of the solutions being such as to deposit on the granules by evaporation of the pentane 1.0 percent of their weight of compound.

Compound! 7 7 0H oH;)ac--cm Compound 13 0H (CH3)aSiCH2-@CH1 l CH2 Compound C (DE cHl)is1cH1-(\ -cm 3)a Compound D 0H (CH1)sSlCH2- CH2Sl(CH3)5 l C(CHs);

Compound E (p CflHgNII'" The melt index of each of the treated samples was then measured according to British Standard 2782, Part 1, 1965, Method C using a 2.16 Kg load, a reservoir temperature of 230C and a 0.0825 in. orifice, the measurements being carried out at periods of 3 minutes and 13 minutes after introduction of the sample into the heated reservoir. Each measurement of the quantity extruded through the orifice was taken over 0.5 minutes and the value obtained converted to give a figure for the prescribed 10 minute extrusion period. The melt index, that is the amount of polypropylene in grams extruded over a 10 minute period, for each of the samples is given in the following table, together with a control measurement carried out on an untreated polypropylene sample.

Compound Melt Index 3 Min. 13 Min. Control 2.1 2.5 A 1.9 2.0 B 2.7 7.4 C 2.9 4.2 d 4.0 11.0 E 2.6 3.9

Compounds A and E were included for comparative purposes and the melt index value for Compound A indicated that it was ineffective in assisting degradation of the polypropylene at 230C. On the other hand Compounds B, C and D all increased the melt index value significantly and were at least as effective as Compound E which is a commercially available peptlser.

Example 2 The compound (CH SiCl-l,Nl-l.C l-l was employed to treat two samples isotactic polypropylene granules in polypropylene.

Measurements of the melt index of the sample containing 0.1 per cent of compound was performed after 3 minutes and 13 minutes in the manner described in Example 1. Values of 2.8 and 5.0 were obtained. When similar measurements were performed after 3 minutes and 4 minutes on the 1.0 per cent sample values of melt index of 2.7 and 20.0 were obtained. When the compound (Cl-1 C CH,NH.Ph was similarly tested at the 0.1 percent level for comparative purposes melt index values of 2.3 and 2.6 were obtained after 3 minutes and 13 minutes respectively.

That which is claimed is:

l. A composition consisting essentially of isotactic polypropylene and from 0.01 to 5 percent by weight, based on the weight of polypropylene, of (a) an organosilane of the general formula A,,Si(CH,NR,) in which R is a hydrogen atom or a monovalent hydrocarbon radical, A represents a radical having from 1 to 18 carbon atoms and is a monovalent hydrocarbon radical, an alkoxy radical, an alkoxyalkyl radical, an alkoxyaryl radical or an alkoxyalkoxy radical and n is 0, l, 2 or 3, or a disiloxane, trisiloxane or tetrasiloxane having therein at least one silicon-bonded group of the general formula CH NR wherein R is as defined hereinabove, any remaining substituents on the silicon atoms being monovalent hydrocarbon radicals, monovalent halogenated hydrocarbon radicalsor oxygen atoms present in siloxane linkages, (b) an organosilicon compound of the general formula wherein R', R" and R' each represent a hydrogen atom, an alkyl radical having up to 18 carbon atoms, an aralkyl radical having up to 18 carbon atoms or a Q SiCl-1, group, wherein Q represents an alkyl, alkenyl or aryl radical having up to 18 carbon atoms, at least one of R, R" and 11" being the Q siCl-l group, or (c) both (a) and (b).

2. A composition as claimed in claim 1 wherein each A represents an alkyl radical having less than 9 carbon atoms or a phenyl radical and n is 3.

3. A composition as claimed in claim 1 wherein each Q is an alkyl radical having less than 9 carbon atoms or a phenyl radical. 

2. A composition as claimed in claim 1 wherein each A represents an alkyl radical having less than 9 carbon atoms or a phenyl radical and n is
 3. 3. A composition as claimed in claim 1 wherein each Q is an alkyl radical having less than 9 carbon atoms or a phenyl radical. 